1. Field of the Invention
The present invention relates to provision of service context in a communication system, and in particular, but not exclusively, to provision of multimedia service contexts in a mobile communication system.
2. Description of the Related Art
A communication system is a facility that enables communication between two or more entities such as user terminal equipment and/or networks entities and other nodes associated with the communication system. The communication may comprise, for example, communication of voice, electronic mail (email), text messages, data, multimedia and so on.
The communication may be provided via fixed line and/or wireless communication interfaces. A feature of the wireless communication systems is that they provide mobility for the users thereof. Examples of communication systems providing wireless communication include the public land mobile network (PLMN) and wireless data networks such a the Wireless Local Area Network (WLAN).
A type of the PLMN is a cellular communication system. In a cellular system the user equipment may access the communication network via access entities known as radio access networks. The skilled person knows the basic operational principles and elements of a cellular network and these are therefore not explained herein in any greater detail. It is sufficient to note that a cell can be defined as an radio access entity that is served by one or several base stations (BS) serving user equipment (UE) via a wireless interface between the base station and the user equipment. Examples of the cellular networks include networks that are based on access systems such as the CDMA (Code Division Multiple Access), WCDMA (Wide-band CDMA), TDMA (Time Division Multiple Access), FDMA (Frequency Division Multiple Access), or SDMA (Space Division Multiple Access) and hybrids thereof.
A communication system typically operates in accordance with a given standard or specification which sets out what the various elements of the system are permitted to do and how that should be achieved. For example, the standard or specification may define if the user, or more precisely, user equipment is provided with a circuit switched service or a packet switched service or both. Communication protocols and/or parameters which shall be used for the connection are also typically defined. For example, the manner how communication shall be implemented between the user equipment and the elements of the communication network is typically based on a predefined communication protocol. In other words, a specific set of “rules” on which the communication can be based on needs to be defined to enable the user equipment to communicate via the communication system.
Standardization of the so called multicast/broadcast multimedia service (MBMS) has been started by the third Generation Partnership Project (3GPP). Multimedia Broadcast/Multicast Service (MBMS) is at present specified in the 3GPP release 6 (R6). More specific details of the MBMS may be found, for example, in the 3GPP technical specification TS22.146 or 3GPP TS25.346 ‘Introduction of the Multimedia Broadcast Multicast Service (MBMS) in the Radio Access Network’.
The latter is a standard associated with the provision of multimedia services in mobile communication systems. Such broadcasts may be provided on a point-to-multipoint channel, i.e. a shared channel from the network to multiple user equipment, or on a point-to-point channel, i.e. on a dedicated channel from the network to each user equipment.
In order to get common understanding of the principles to define the multicast/broadcast multimedia service (MBMS) architecture and the procedures, some basic assumptions have been made this far. In accordance with the present thinking a controlling radio network controller (CRNC) such as a radio network controller (RNC) controlling one or more cells is assumed to maintain one MBMS context per established multicast/broadcast multimedia service (MBMS). This is applied for each CRNC within a MBMS serving area. Each controlling radio network controller (CRNC) multicast/broadcast multimedia service (MBMS) context (CRNC MBMS context) is thus associated with a single MBMS service ID. The CRNC MBMS context can be associated with a list of user equipment (UE) in connected mode. The list includes those user equipment (UEs) that are present in each cell controlled by the CRNC and have activated a MBMS service. In addition, the CRNC MBMS context can be established when the radio access bearer (RAB) for the MBMS is established between the radio network controller (RNC) and the serving GPRS support node (SGSN; General Packet Radio Network) for a specific multicast/broadcast multimedia service (MBMS). It is also assumed that only one information flow over the Iu-interface between a radio network controller and the core network is provided for the radio network controller (RNC) per established multicast/broadcast multimedia service (MBMS). Thus, each user equipment (UE) in connected mode with an activated multicast/broadcast multimedia service (MBMS) has its user equipment (UE) context bind to the radio access bearer (RAB) for this multicast/broadcast multimedia service (MBMS).
The current MBMS proposal assumes that that two different types of MBMS contexts will be possible in the MBMS. These proposed context types are MBMS service specific “MBMS service context” and user equipment (UE) specific “MBMS UE context”.
It is not necessary for the user equipment to join any of the MBMS broadcast services in order to receive them. However, each user equipment has to join the MBMS service in order to receive multicast. In a typical case the “joining” shall be understood such that before the reception of the MBMS session the user equipment must go through the so called “Join” procedure, upon which the user equipment indicates its willingness to receive the MBMS service session. This phase is typically performed by using the point-to-point connection and therefore it is secured. This allows sending of session specific parameters in secure form. The following will relate to service contexts that require the user equipment to join them.
It has been agreed in the 3GPP that the user equipment (UE) may join an MBMS service by sending an IGMP ‘Join’ message to the Gateway General Packet Radio Service (GPRS) Support Node (GGSN). IGMP (Internet Group Management Protocol) is a well known protocol defined by the Internet Engineering Task Force (IETF). The UE also signals with the Serving GPRS Support Node (SGSN) to activate an MBMS UE context. When the user equipment joins the service, the above referenced MBMS service contexts and MBMS UE contexts are created in the appropriate GGSN/SGSN entities.
It has been proposed that a Radio Access Network Application Part (RANAP) signaling message is sent from the SGSN to the RNC per each joined Packet Mobility Management connected (PMM-CONNECTED) user equipment. However, the Inventors have found that this may create substantial amount of signaling, especially if the services prove to be hugely popular among the mobile users.
The UE may also leave the MBMS service it has joined earlier. However there are no common rules for the procedure to leave. A proposal is that the MBMS UE context is removed all together at the time of a user equipment leaving the service. Another proposal is that the MBMS service context could be removed when the MBMS data transmission is over. The removal can be accomplished in response to a notification from a multimedia service content provider entity such as Broadcast/Multicast Service Center (BM-SC) that the MBMS service is over.
However, such inflexible removal of the MBMS contexts may cause problems. For example, if a new user equipment joins the MBMS service context during a MBMS data transmission from which the MBMS service context has been removed, the MBMS service context has to be created again in appropriate GGSN/SGSN entities. This may result in unnecessary signaling at MBMS service context removal and re-creation operations.
Furthermore, if all joined user equipment are leaving the service substantially at the same time when a new user equipment wants to join, the MBMS service context may become removed despite the new willing user.
The network entities involved in the service provisioning need to be informed about any new user equipment and/or any removed user equipment. Information regarding changes in the status of user equipment may also need to be passed between the entities of the core and radio access networks. This may cause a substantial amount of signaling between the radio access network and the core network that is caused by reports regarding changes in the service status or other information of individual user equipment.